Matteo Ciccotti | ESPCI ParisTech (original) (raw)

Papers by Matteo Ciccotti

$Research paper thumbnail of Roughness of oxide glass sub-critical fracture surfaces$

HAL (Le Centre pour la Communication Scientifique Directe), Jul 24, 2018

An original setup combining a very stable loading stage, an atomic force microscope and an enviro... more An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable sub-critical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self-affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The 2 roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al. [1] on the effect of the material's heterogeneity on the crack tip stresses with the self-affine nature of the fracture surfaces.

Macromolecules, Oct 10, 2019

For decades, poly(vinylbutyral) (PVB) has been the polymer of choice to improve the impact resist... more For decades, poly(vinylbutyral) (PVB) has been the polymer of choice to improve the impact resistance of laminated glass. PVB presents large rupture strain, large tensile strength and excellent dissipative properties. Here we investigate the relation between macromolecular structure and mechanical properties of plasticised PVB by combining large strain tensile experiments with calorimetry, X-ray and birefringence measurements. We find that the mechanical response is dominated by creep and that this plastic-like flow can effectively be described by a strain dependent viscosity. The commonalities with other toughened polymeric materials are outlined, and especially the role played by phase separated domains with weaker physical bonds. These results could help optimize polymer design for toughness and impact applications.

Journal of polymer science, Mar 21, 2021

We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial t... more We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU.

Polymer Testing, May 1, 2021

Thermoplastic polyurethane elastomers (TPU) are stretchable, tough, wear resistant and easily pro... more Thermoplastic polyurethane elastomers (TPU) are stretchable, tough, wear resistant and easily processable soft materials. Especially because of their recyclability, TPUs can be suitable candidates to replace rubbers in several applications such as damping, footwear and cable coatings. However, their capacity to operate under cyclic loads over many cycles was rarely investigated, mainly due to their complex strain-dependent morphology and viscoplastic character. Additionally, the absence of chemical crosslinks results in a certain degree of creep and plastic deformation when TPUs are cyclically strained, questioning how to unambiguously define fracture mechanics variables such as the energy release rate G, typically used to evaluate fatigue crack growth in chemically crosslinked elastomers. We show that, when TPUs are cyclically loaded up to the same value of maximum stretch, their stress-stretch curve changes with the number of applied cycles, but eventually achieves a steady-state. We propose a suitable methodology to evaluate the cyclic fatigue resistance in TPUs, based on a fracture mechanics approach with some additional treatments to account for the higher tendency to creep of TPUs than thermoset rubbers. Comparing the obtained results of TPU with those for classical filled rubbers with a similar small strain modulus, we underline the excellent toughness and cyclic fatigue resistance of TPUs, opening new opportunities in their use for applications requiring to resist to crack propagation under cyclic loading at large strains.

Glass structures & engineering, Sep 9, 2020

When laminated glass shatters under impact, most of the energy dissipation occurs in the coupled ... more When laminated glass shatters under impact, most of the energy dissipation occurs in the coupled delamination and stretching of the polymer interlayer between broken chunks of glass. The strong dependency of these mechanisms on interlayer nature, on loading rate and on temperature has been previously investigated: however, the effect of the interfacial adhesion is unexplored. In this work, a surface modification technique is proposed, along with a mechanical characterization of the debonding with the Through Crack Tensile Test. We show that while increasing adhesion has the effect of enhancing the energy required to propagate the delamination fronts as well as the stretch level of the delaminated interlayer, the dissipation associated to the stretching of the volume of the PVB interlayer seems unaffected. We attribute this effect to the competition between the changes in both stretch and stretch rate in the viscoelastic interlayer. Finally, we discuss the experimental observation of the limits of the steady-state debonding regime, related to the competition between adhesive crack propagation and cohesive failure in the interlayer.

HAL (Le Centre pour la Communication Scientifique Directe), Dec 23, 2008

The present review is intended to revisit the advances and debates in the comprehension of the me... more The present review is intended to revisit the advances and debates in the comprehension of the mechanisms of subcritical crack propagation in silicate glasses almost a century after its initial developments. Glass has inspired the initial insights of Griffith into the origin of brittleness and the ensuing development of modern fracture mechanics. Yet, through the decades the real nature of the fundamental mechanisms of crack propagation in glass has escaped a clear comprehension which could gather general agreement on subtle problems such as the role of plasticity, the role of the glass composition, the environmental condition at the crack tip and its relation to the complex mechanisms of corrosion and leaching. The different processes are analysed here with a special focus on their relevant space and time scales in order to question their domain of action and their contribution in both the kinetic laws and the energetic aspects.

Science Advances, Oct 15, 2021

Although elastomers often experience 10 to 100 million cycles before failure, there is now a limi... more Although elastomers often experience 10 to 100 million cycles before failure, there is now a limited understanding of their resistance to fatigue crack propagation. We tagged soft and tough double-network elastomers with mechanofluorescent probes and quantified damage by sacrificial bond scission after crack propagation under cyclic and monotonic loading. Damage along fracture surfaces and its spatial localization depend on the elastomer design, as well as on the applied load (i.e., cyclic or monotonic). The key result is that reversible elasticity and strain hardening at low and intermediate strains dictates fatigue resistance, whereas energy dissipation at high strains controls toughness. This information serves to engineer fatigue-resistant elastomers, understand fracture mechanisms, and reduce the environmental footprint of the polymer industry.

Reports on Progress in Physics, Mar 23, 2016

Soft Materials are materials with a low shear modulus relative to their bulk modulus and where el... more Soft Materials are materials with a low shear modulus relative to their bulk modulus and where elastic restoring forces are mainly of entropic origin. A sparse population of strong bonds connects molecules together and prevents macroscopic flow. In this review we discuss the current state of the art on how these soft materials break and detach from solid surfaces. We focus on how stresses and strains are localized near the fracture plane and how elastic energy can flow from the bulk of the material to the crack tip. Adhesion of pressure-sensitive-adhesives, fracture of gels and rubbers are specifically addressed and the key concepts are pointed out. We define the important length scales in the problem and in particular the elasto-adhesive length Γ/E where Γ is the fracture energy and E is the elastic modulus, and how the ratio between sample size and Γ/E controls the fracture mechanisms. Theoretical concepts bridging solid mechanics and polymer physics are rationalized and illustrated by micromechanical experiments and mechanisms of fracture are described in detail. Open question and emerging concepts are discussed at the end of the review.

Zenodo (CERN European Organization for Nuclear Research), Apr 19, 2022

Soft Matter, 2017

In the dynamic rupture of laminated glass, it is essential to maximize energy dissipation. To inv... more In the dynamic rupture of laminated glass, it is essential to maximize energy dissipation. To investigate the mechanisms of energy dissipation we have experimentally studied the delamination and stretching of a polymeric viscoelastic interlayer sandwiched between glass plates. We find that there is a velocity and temperature domain in which delamination fronts propagate in a steady state manner. At lower velocities, fronts are unstable while at higher velocities, the polymer ruptures. Studying the influence of the interlayer thickness, we have shown that the macroscopic work of fracture during the delamination of the interlayer can be divided in two main components: 1. A near crack work of fracture which is related to the interfacial rupture and to the polymer deformation in the crack vicinity. 2. A bulk stretching work which relates to the stretching of the interlayer behind the delamination front. Digital Image Correlation measurements showed that the characteristic length scale over which this stretching occurs is of the order of the interlayer thickness. Finally, an estimate of the bulk stretching work was provided, based on a simple uniaxial tensile test.

Soft Matter, 2020

The performances of Pressure Sensitive Adhesives (PSA) are generally evaluated using different lo... more The performances of Pressure Sensitive Adhesives (PSA) are generally evaluated using different loading geometries such as tack, peel and shear tests. It is difficult to link the behaviors of PSAs in these different geometries, and to predict the result of one test from another, because the confinement of a soft and dissipative material prevents the use of standard fracture mechanics, which separates the interface debonding behavior from the dissipation associated with the bulk deformation. We present here an original experimental investigation based on the modeling strategy proposed by Creton and Ciccotti[1]. Using instrumented versions of both peel and tack measurements, we compared the adherence performances of a series of model PSAs based on styrene-isoprene block copolymers, while identifying the mesoscale mechanisms at play during debonding. This analysis method allows us to model the contribution of the large strain rheology of the PSAs in the total work of debonding. We clearly show that both the adherence performances and local mechanisms can be closely related between peel and tack when considering both similar confinement and a similar strain rate of the fibrils that are spontaneously formed during debonding. While the overall adherence properties change by a factor of 3 between the different samples, the peel tests only present a minor +20% bias in adherence, which can be attributed to the combination of a 10% increase in the average stress and a 10% increase in the maximum strain of the fibrils. This improvement in the understanding of the PSA performances opens the way to a more sound mechanical design of PSA based joints.

International Journal of Fracture, Nov 23, 2016

The debonding of Pressure Sensitive Adhesives (PSA) is a classical example of the difficult and u... more The debonding of Pressure Sensitive Adhesives (PSA) is a classical example of the difficult and unsolved issue of fracture in soft viscoelastic confined materials. The presence of a complex debonding region where the adhesive undergoes cavitation and the very large strain of a spontaneously formed fibrillar network has defied many modeling attempts over the past 70 years. We present here a novel technique to provide an accurate measurement of the local large strain response of the fibrillar debonding region during the steady-state peeling of a well known commercial adhesive over a wide range of peeling velocity and angle. The technique is based on high resolution imaging of the debonding region during peeling and is coupled to a cohesive zone modeling of the adhesive interaction between the flexible tape backing and the rigid substrate. The resulting database provides a strong ground for validating and further developing models (Villey et al. 2015) aiming to capture the effects of both geometry and non-linear adhesive rheology on the exceptional adherence energy of PSAs.

Macromolecules, Oct 22, 2018

We investigate experimentally the adherence energy Γ of model polyacrylate Pressure Sensitive Adh... more We investigate experimentally the adherence energy Γ of model polyacrylate Pressure Sensitive Adhesives (PSAs) with combined large strain rheological measurements in uniaxial extension and an instrumented peel test. We develop a nonlinear model for such peel test which captures the dependence of Γ(V) with peeling rate V revealing the key role played by the extensional rheology. Our model explains in particular why traditional linear viscoelastic approaches correctly predict the slope of Γ(V) curves for sufficiently elastic PSAs characterized by a simple rate-independent debonding cri-1 terion. However, for more viscoelastic adhesives, we identified a more complex ratedependent debonding criterion yielding a significant modification of the Γ(V) curves, an effect that has been largely overlooked so far. This investigation opens the way towards the understanding of fibrils debonding, which is the main missing block to predict the adherence of PSAs.

Physical Review Letters, Apr 25, 2008

We study the equilibrium properties of a liquid phase condensed at the nanoscale between the surf... more We study the equilibrium properties of a liquid phase condensed at the nanoscale between the surfaces of a sharp crack in fused silica in a moist controlled atmosphere. The extension of the condensed phase along the fracture is measured by in situ atomic force microscopy phase imaging and it is shown to be determined by a critical distance between the opposite crack surfaces, which is an increasing function of humidity. The present technique is very promising for measuring the properties of confined liquids at the nanoscale as well as for modeling the physics and chemistry of slow crack propagation in glasses.

DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2020

In laminated glass under impact, most of the energy dissipation occurs in the coupled delaminatio... more In laminated glass under impact, most of the energy dissipation occurs in the coupled delamination and deformation of the polymer interlayer. The strong dependency of these mechanisms on interlayer nature, on loading rate and on temperature is known: however, the effect of the interfacial adhesion is unexplored. In this work, a surface modification technique is proposed, along with a mechanical characterization of the debonding with the Through Crack Tensile Test. We show that changing adhesion mostly affects dissipation close to the delamination front, while dissipation in the volume of the PVB interlayer seems unaffected, which we attribute to the competition between the changes in both strain and strain rate in the viscoelastic interlayer. Finally, we discuss the experimental observation of the limits of the steady-state debonding regime, related to the competition between adhesive crack propagation and cohesive failure in the interlayer.

Bulletin of the American Physical Society, Mar 2, 2020

Extreme Mechanics Letters, Oct 1, 2019

Springer eBooks, 2020

Fracture propagation is inherently a multiscale problem, involving the coupling of many length sc... more Fracture propagation is inherently a multiscale problem, involving the coupling of many length scales from sample dimension to molecular level. Fracture mechanics provides a valuable link between the macroscopic scale of the structural loading of the samples and the scale of the process zone for brittle materials. Modeling the toughness of materials requires yet an investigation at scales smaller than this process zone, which is nanometric in oxide glasses and micrometric in polymer glasses. We present here the important insights that have